Semiconductor wafer processing in the fabrication of integrated circuitry typically includes the formation of contact openings within insulating layers to underlying conductive structures. Currently, such processing is typically conducted by photolithography wherein a masking layer is deposited and a desired pattern of openings is formed therethrough. The masking layer is then used as a mask while chemical etching is conducted through the mask openings into the underlying insulative material to etch it largely selective to the masking layer such that the openings can be extended through the insulating material to the conductive structures therebeneath.
The intent, of course, is to very precisely align the reticle or other device used to form the desired opening patterns within the masking layer. If the openings are misaligned, the openings to be etched within the insulating layer(s) might include portions which extend laterally beyond the desired boundary of the conductive structure to which the openings are being etched. This can undesirably lead to etching of insulating material laterally of the conductive structure and sometimes lead to undesired exposure of other conductive structures. When the contact openings are filled with conductive material, this can of course lead to fatal shorts in the circuitry.
One prior art method of minimizing or attempting to prevent this tendency is to provide a thin blanket etch stop layer over the conductive structure prior to providing a thicker insulative material layer through which the primary contacts are intended to be made to the conductive structures. However, another masking step is typically utilized to make contact openings within the etch stop layer prior to provision of the thicker insulative layer thereover. The typical thin nature of the blanket deposited and photopatterned etch stop layer is such that a chemistry can typically be selected to etch the etch stop layer largely selective relative to the underlying conductive material and other insulative material beneath the etch stop layer. Subsequently, the etch stop layer will provide a degree of protection for mis-aligned contact openings being etched into the overlying insulative layer.
The following invention was motivated in addressing the above identified problems, although such is in no way so limited. The invention is limited only by the accompanying claims as literally worded without limiting reference to the specification, and in accordance with the doctrine of equivalence.